The major objective of this research project is to study in greater detail the neural organization of primate oculomotor system. A microelectrode technique is utilized to record the activity of single neurons in the brain stem of fully alert, behaving monkeys coupled with a sensitive, drift-free magnetic field method of measuring eye movements. The proposed work will focus on two important supranuclear areas that project directly to oculomotor neurons, the vestibular nuclei (VN) and the medial pontine reticular formation (MPRF). (1) A significant group of eye movement-related neurons with burst-tonic behavior have been previously described in VN and in lesser numbers in MPRF. These neurons in VN have been shown to be disynaptically connected to the vestibular nerves. The vestibular synaptic connections to MPRF burst-tonic neurons will be explored with chronically implanted electrodes located in the vestibular nerves. The results will be compared to those obtained from VN eye movement-related neurons to test the idea that these two pools of cells form a single interconnected network of functionally similar units. (2) The origin of visuomotor signals to both VN and MPRF eye movement-related neurons will be explored by chronically implanting an array of stimulating electrodes on the superior colliculus. The possible spatially coded input from the colliculus to each type of eye movement-related brain stem neuron will be studied during vergence eye movements. BIBLIOGRAPHIC REFERENCES: Keller, E.L. and Daniels, P.D., "Oculomotor related interaction of vestibular and visual stimulation in vestibular nucleus cells in alert monkey," Exptl. Neurol. 46:187-198, 1975. Keller, E.L., "Vestibular nucleus neurons correlated with visually guided eye movements. Synaptic connections," Spring Meeting Proc. ARVO, 92, 1975.